How to create a trigger that update the date field and time field upon modify of the row?

I have created a table testtable inside the database testbase that have the following structure: product_no (int, not null) product_name (varchar(30), not null) price (money, null) expire_date (date, null) expire_time (time(7), null) However, how do I write a trigger such that it will update that particular row that has been modified (or updated with new information) and record the modification date into the expire_date field and the modification time into the expire_time field? (or if this is possible?)